The #Hubble gyros are very interesting to me. They apparently contain a thick sauce, er, sorry, liquid inside a wrapper of pida, no – titanium, yes titanium. There are onions, or rather wires that go through the garlic sauce, I mean liquid, and those are at continual risk.
Someone should investigate, and I'll gladly volunteer.
NASA confirms that #Hubble will switch to one-gyroscope mode after the increasingly erratic behavior of gyro 3 caused the observatory to repeatedly go into safe mode.
Hubble will continue doing great science, but with somewhat reduced efficiency. It will need more time to slew and lock onto science targets. There is also a limit to the fraction of the sky it can observe at any one time (although it will have access to the full sky over the course of a year).
I'm glad that switching #Hubble to single-gyro pointing was not necessary until now; because the telescope did important observations of the #DARTMission impact and its aftermath through last year.
As we suspected, the NASA Hubble team has decided to operate Hubble henceforth in single gyro mode.
There are some limitations in this mode - Hubble will need more time to slew and lock onto a science target and won't have as much flexibility as to where it can observe at any given time.
The other healthy gyro will be kept as a spare. Hubble now has 4 failed gyros.
The team expects to resume science operations again by mid-June.
Note that gyros are used to accurately determine Hubble's pointing direction. Telescope movement is done using reaction wheels and magnetic torquers.
In one-gyro mode, Hubble supplements info from the gyro with info from its magnetometers, sun sensors, star trackers and fine guidance sensors + some nifty software processing. It's a slower process but once Hubble is on target, pointing accuracy is comparable to that of 3-gyro mode.
Modern spacecraft like JWST use a newer type of gyroscope - the "Hemispherical Resonator Gyroscope" (HRG). It uses a quartz hemisphere vibrating at its resonant frequency in a vacuum; the hemisphere's rate of motion is sensed by the interaction between the hemisphere and sensing electrodes on the HRG housing.
There are no moving parts, flexible leads or bearings.
Extremely reliable but high mfg complexity.
MTBF = 10 million hours!
Hubble's gyros contain a wheel spinning at 19,200 rpm on gas bearings. The wheel is mounted in a sealed cylinder, which floats in a thick fluid. The gyro’s motor is powered via hair-thin wires that traverse this fluid.
Rotations of the spacecraft cause tiny movements of the axis of the wheel, which are measured and fed to Hubble’s flight computer.
Hubble's gyros were the most accurate in the world in their time. But prone to failure ...